On the recognition of Yersinia protein tyrosine phosphatase by carboxylic acid derivatives

Some members of Yersinia (Y), a genus of bacteria in the family Yersiniaceae, are pathogenic in humans, causing a range of health problems, from gastrointestinal syndromes to the plague. The Y protein tyrosine phosphatase (PTP) YopH is a crucial virulence determinant, considering the vital roles of PTPs in the intracellular signal transduction pathways and cell cycle control. The structural understanding of YopH as a cellular target in pathogenic conditions caused by Y infection is a prerequisite for designing potent and selective YopH inhibitors. Thus, by using molecular docking simulations, the open and closed conformations of the so-called 'WPD loop' (352-Gly-Asn-Trp-Pro-Asp-Gln-Thr-Ala-Val-Ser-361), located nearby the active site (403-Cys-Arg-Ala-Gly-Val-Gly-Arg-Thr-410) in YopH structure, are shown to be relevant for recognition by carboxylic acid derivatives, and the closed conformation is a more preferable receptor in terms of the quantitative correlation with experimental data. In both cases, aurintricarboxylic acid (ATA) has the greatest affinity to YopH. Consequently, a quantum mechanics/molecular mechanics (QM/MM) molecular model is derived to see into the extent of the ATA-induced open-closed conformational change. Active site residues and the WPD loop, as well as ATA are treated using SCC-DFTB-D (QM level), while the rest of the complex is treated using AMBER force field (MM level). The active/inactive functional behavior of YopH is explored by observing the interaction mode of ATA with the wild-type (wt)/Cys403Ser receptor and evaluating the competitive inhibition parameters. Implications of the present study for experimental research are discussed. Communicated by Ramaswamy H. Sarma.

Bi Metal-Organic Framework (Ce/Ni-BTC) as Heterogeneous Catalyst for the Green Synthesis of Substituted Chromeno[4, 3-b]quinolone under Solvent Free Condition

AIMS

Novel bi metal organic framework (b-MOF) is synthesized and used as a heterogeneous catalyst for the synthesis of chromeno[4, 3-b]quinolone derivatives via one-pot and solvent-free, four-component reaction of dimedone, aromatic aldehydes, 4-hydroxycoumarin and ammonium acetate at 110°C.

BACKGROUND

b-MOFs can be used as a heterogeneous catalyst in the synthesis of many organic compounds. The active and multi-purpose sites in b-MOFs provide a varied function in their catalytic applications. In this paper, reductive CES method is applied for the synthesis of Ce_0.47/Ni_0.53-BTC b-MOF. The resulting b-MOF was used as a heterogeneous catalyst for the synthesis of chromeno[4, 3-b]quinolone via one-pot and solvent-free, fourcomponent reaction of dimedone, aromatic aldehyde, 4-hydroxycoumarin and ammonium acetate at 110 °C.

METHOD

Ce_0.47/Ni_0.53-BTC was synthesized in an electrochemical cell composed of a stainless steel foil with a size of 5cm×5cm centered between two 5cm×5cm sized graphite plates as the anodes by the cathodic current density of 0.2 A/dm² and placed in a solution of cerium nitrate (0.3 g), nickel nitrate (0.3 g), H₃BTC (0.2 g) and NaNO₃ (0.1 g) in ethanol (500 mL). Ce_0.47/Ni_0.53-BTC (10 mg) was added to a mixture of dimedone (1 mmol), aromatic aldehyde (1 mmol), hydroxycoumarin (1 mmol) and ammonium acetate (1.5 mmol) and stirred at 110 °C under solvent-free conditions for 45 min. The reaction evolution was controlled by the TLC (hexane:ethyl acetate, 4:1). Then, boiling ethanol was added to the reaction mixture and stirred at room temperature for 15 min. After the reaction completion, the catalyst was separated by centrifuge. Finally, the reaction mixture was placed in an ice bath, which resulted in a white solid product and recrystallized from ethanol to give the pure product.

RESULT

The b-MOF catalyst showed very good efficiency in the synthesis of the desired compounds and can be easily recovered by centrifuge and reused at least five times without a decrease in catalytic activity.

CONCLUSION

In this report, a novel bi metal-organic framework (Ce0.47/Ni0.53-BTC) is synthesized via the cathodic electrosynthesis method. The synthesized b-MOF is fully characterized by several characterization methods. The catalytic activity of Ce0.47/Ni0.53-BTC is investigated in the synthesis of chromeno[4, 3-b]quinolone derivatives via one-pot four-component reaction of dimedone, aromatic aldehyde, 4-hydroxycoumarin and ammonium acetate. The reaction optimization results showed that the highest isolated yield was obtained when the reaction was performed in solvent-free conditions at 110 °C. The catalyst showed to be highly efficient in the synthesis of the desired compounds and performing the reaction utilizing various starting materials gave the products in good isolated yields, which proves the generality and the scope of the method. The catalyst could easily be recovered by centrifuge and reused at least five times without a decrease in catalytic activity.

Intercepted-Knoevenagel condensation for the synthesis of unsymmetrical fused-tricyclic 4H-pyrans

4H-Pyrans (4H-Pys) and 1,4-dihydropyridines (1,4-DHPs) are important classes of heterocyclic scaffolds in medicinal chemistry. Herein, an indium(III)-catalyzed one-pot domino reaction for the synthesis of highly functionalized 4H-Pys, and a model of 1,4-DHP is reported. This alternative approach to the challenging Hantzsch 4-component reaction enables the synthesis of fused-tricyclic heterocycles, and the mechanistic studies underline the importance of an intercepted-Knoevenagel adduct to achieve higher chemoselectivity towards these types of unsymmetrical heterocycles.

A One-Pot, Three-Component, Solvent-Free Synthesis of Novel 6H-Chromeno[3’,4’:5,6]Pyrido[2,3-d]Pyrimidine-Triones under Microwave Irradiation

A green and efficient method for preparing novel heterocyclic systems is established through the reaction of differently substituted benzaldehydes, barbituric acid and 4-amino-2H-chromene-2-one under solvent-free conditions. This method affords 6H-chromeno[3’,4’:5,6] pyrido[2,3-d]pyrimidine-trione derivatives in high yields and short reaction times.

High quantum yield and pH sensitive fluorescence dyes based on coumarin derivatives: fluorescence characteristics and theoretical study

The fluorescence coumarin derivatives were synthesized by an efficient one-pot, three-component reaction in 80–90% yields.